Traditionally, long-haul truck-tractor vehicles 10, as shown in FIG. 2, are configured with sleeper units 11 which provide sleeping accommodation for truck operators during long hauls. Vehicle 10 is operated from a cab unit 12 (i.e., the driving compartment) which is positioned forward of sleeper unit 11. Generally, these cab and sleeper assemblies are constructed as either a structurally integral cab and sleeper assembly 14' (FIG. 2) or as separate cab and sleeper units 14 and 14" (FIGS. 1 and 3).
Separate cab and sleeper assemblies 14 and 14", are highly desirable since these configurations are capable of being constructed independent of one another which fosters configuration flexibility. Thus, these units are capable of different cab and sleeper configurations to suit customer needs. The sleeper unit 11, for example, may be purchased in a variety of lengths, heights, compartment layouts or the like. By comparison, the highly tooled cab unit 12 may remain unchanged and mounted to chassis frame 15.
Sleeper unit 11 is generally mounted to chassis frame member 15 at three discrete mounts 16. Chassis frame member 15, briefly, includes two longitudinally extending beams 25 positioned in a side-by-side spaced-apart relation which are coupled together by a plurality of transversely positioned cross-beams 26. Typically, two transversely spaced-apart front rubber mounts 16 coupled sleeper unit 11 to each longitudinal beam 25, respectively. A single rear rubber mount 16 positioned intermediate a rear portion of sleeper mount 11 and mounted to one cross-beam 26.
Cab unit 12 (i.e., the driving compartment) is positioned forward of sleeper unit 11 and is similarly mounted to chassis frame member 15 at three discrete mounts 16 which provide limited isolation from chassis frame member 15. To access sleeper unit 11 from cab unit 12, aligned ports or openings (not shown) are provided which extend through both cab rear wall 17 and the adjacent sleeper front wall 18. A rubber boot 19 spans the interface between cab unit 12 and sleeper unit 11 to seal assembly 14 and to provide weather protection.
This arrangement affords other benefits as well. Because sleeper unit 11 is often taller and wider than adjacent cab unit 12, crash damage during frontal impacts, roll-overs or jack-knifes is more confined to sleeper unit 11. Thus, repair to vehicle 10 may be more concentrated on the damaged portion (i.e., the sleeper unit) rather than also requiring removal or repair of overall cab and sleeper assembly 14 or cab 12. Non-productive time is minimized and repair costs are reduced, especially when considering the substantial complexity of cab unit 12.
However, by providing independent cab and sleeper units, it is more difficult to provide vibration and motion isolation of those units from chassis frame 15. Hence, the ride quality of each respective unit is compromised. The relatively short longitudinal span between the front and rear mounts 16 of each unit 11, 12 (FIG. 1) causes them to experience violent pitch motions. Individual cab and sleeper units 11, 12 yaw, pitch, roll, heave, surge and slip in directions opposite one another. Such relative motion therebetween necessitates the application of fairly flexible rubber boot joints 19, as set forth above. Despite their flexibility, these joints 19 can still be damaged which jeopardizes seal integrity. Further, wire harnesses, hoses, tubes or the like, extending between cab unit 12 and sleeper unit 11 must be designed for substantial mobility which increases the likelihood of component failure.
In one attempt to improve ride quality for separate cab and sleeper unit assembly 14, a pneumatic suspension component 20 with roll compliance replaces rear rubber mount 16 between chassis frame 15 and rear portions of individual units 11, 12 to provide better dampening. However, compliance of pneumatic suspension component 20 may be impeded because of the interfacing rubber boot 19 extending between cab rear wall 17 and sleeper front wall 18. Although rubber boot 19 is flexible in some directions, it is stiff enough to interfere with the independence of rear mounted pneumatic suspension component 20 as relative deflections between cab rear wall 17 and sleeper front wall 18 occur. Such interference greatly reduces the isolation performance and the effectiveness of the suspension. Another technique employed to improve ride quality is to structurally integrate cab unit 12' with sleeper unit 11', as may be viewed in FIG. 2. Since integral structure is essentially a composite between the cab and sleeper unit, the overall structure mass is increased compared to either independent unit by itself. Further, the longer integral unit span, relative a longitudinal axis extending through integral cab and sleeper assembly 14', increases the moment of inertia about axes perpendicular to the longitudinal axis. A greater moment of inertia about these perpendicular axes tends to resist pitch movement thereabout which results in improved ride quality. Moreover, pneumatic suspension components 20 positioned proximate the rear of sleeper portion 11' can perform effectively without interference.
While these integral assemblies 14' have been adequate to improve ride quality in both the cab and sleeper portions, several problems are associated with these integral designs. The integral cab and sleeper assembly 14' precludes the modularity aspect which is highly desirable to both the manufacturer and the vehicle owner. Crash damage to the integral unit will not be confined to either cab unit 12' or sleeper unit 11'. Rather, structural damage will likely extend throughout the entire integral assembly. Further, cab and sleeper configuration selection is generally reduced. Moreover, the sleeper portion of the integral unit cannot be separated from the cab portion should the vehicle operator or owner choose to convert the truck-tractor vehicle to other than long-haul vocations.
Hybrid modular cab and sleeper unit assemblies 14", as shown in FIG. 3, have been developed which retain separate cab and sleeper units while improving ride quality. Typically, these modular cab and sleeper assemblies 14" incorporate an elongated sub-frame 21" in which both cab unit 12" and sleeper unit 11" are rigidly mounted thereto and carried thereon to form a carriage assembly. Further, sleeper unit 11" and cab unit 12" may include opposing aligned flange portions 24" and 25" circumferentially positioned about the periphery of the interface opening therebetween which permit coupling of the units together at a plurality of locations. As shown in FIG. 3, a plurality of spaced-apart bolts 23" extend through and couple opposing flanges 24" and 25".
This carriage assembly is then mounted to chassis frame 15" at three or four discrete locations (i.e. rubber mounts 16") between sub-frame 21" and chassis frame 15". Hence, the longitudinal span between mounts 16" can be increased which reduces violent pitch motions, as above indicated. Moreover, isolation may further be improved by incorporating a pneumatic suspension component 20" with roll compliance at the rear portion of sub-frame 21".
This hybrid configuration (FIG. 3), however, is also inherent with associated design problems. Addition of sub-frame 21" substantially increases the overall weight of composite structure 14", which reduces operation efficiency. This configuration, further, impairs modularity since removal and installation of all peripheral bolts 23" is laboriously required. Conversion to "no-sleeper" vocations is also severely impeded since removal of sleeper unit 11" also requires removal of subframe 21". Finally, subframe 21" increases the overall ride height of assembly 14".